Wednesday, May 18, 2011

Catalyst 6500 12.2(33)SXH EtherChannel Hash-Distribution Algorithm

Cisco IOS releases earlier than 12.2(33)SXH support a load-distribution algorithm called the fixed algorithm.
When a switch port is being added to or deleted from an EtherChannel, the switch updates the port ASIC for each switch port in the EtherChannel and causes a short outage on each port.

Cisco IOS Release 12.2(33)SXH and later support an additional algorithm called the adaptive algorithm.
The adaptive algorithm does not need to update the port ASIC for existing member switch ports.

The fixed algorithm is the default algorithm.
The adaptive algorithm can be configured globally or for individual port channels.
The change of the algorithm is applied upon the next member link event, eg: link down, link up, addition, deletion, no shutdown, and shutdown.
The command console would issue the following warning message upon issuing the port-channel hash-distribution {adaptive | fixed} global configuration command or interface subcommand indicating that the algorithm change only takes effect upon the next member link event.Note: No warning message is observed as claimed on 12.2(33)SXH and 12.2(33)SXI releases.